The long-term objective of this research is to define the molecular mechanism of dysfunctional apoptosome activation in epithelial ovarian carcinoma. This may lead to the identification of novel molecular targets for the treatment of ovarian cancer. This project is intended to contribute toward the long-term goal by testing the hypothesis that PHAPI, a tumor suppressor, plays a critical role in the regulation of apoptosome activation in ovarian cancer. The career development plan of this proposal is directed at promoting scientific independence of the candidate through interactions with established investigators in related fields. Alterations in the regulation of apoptosis may contribute to the pathogenesis of cancer and resistance of tumor cells to chemotherapy. In mammalian cells, non-receptor mediated apoptosis occurs predominantly via assembly of a cytochrome c dependent apoptosome complex containing caspase-9 and Apaf-1. We have shown that cytosolic extracts from human ovarian carcinoma cell lines and primary ovarian tumor samples are deficient in their ability to assemble and activate the apoptosome complex. Cell lines and tumor samples demonstrating dysfunctional apoptosome activation are associated with resistance to chemotherapy induced apoptosis. The molecular basis for apoptosome dysfunction in ovarian carcinoma appears to be due to an inability to recruit or retain caspase-9 in the apoptosome, and is associated with diminished Apaf-1/caspase-9 binding. PHAPI has been recently described as a facilitator of apoptosome-mediated caspase-9 activation. In an in vitro system, recombinant PHAPI stimulated caspase-3 activation, and induced increased amounts of caspase-9 to associate with the Apaf-1 oligomer. The regulatory role of PHAPI in apoptosis, and the clinical significance of this has not been clearly established. The Specific Aims of this project are to: 1) Correlate expression pattern of PHAPI with apoptosome function in a panel of ovarian carcinoma cell lines and primary ovarian tumor samples. 2) Determine if expression of PHAPI in chemoresistant ovarian carcinoma cell lines can restore apoptosome function. 3) Determine if PHAPI expression is required for apoptosome function in ovarian carcinoma.